Recently I’ve managed to catch multiple rocket launches live thanks to the magic of youtube, I don’t think we’ve had a SpaceX mention recently and they just made a great fireball!
The plan:
Shiney metal rocket goes up and to the side a bit to a specific altitude where it belly flops and uses its wings to fall glide, reducing it’s fall speed and covering the horizontal distance to hover slam land back on to the pad.
The big challenges here are that rockets generally don’t like slowing down, they don’t like lateral movements, and they sure don’t like doing them quickly with liquid fuels sloshing around. The goal of starship’s wing design is reduce the need for heat shielding by entering the atmosphere at a nice long and potentially powered glide.
What happens:
T-0 The rocket doesn’t immediately explode, one hurdle down!
At T 1:40 and T 3:12 we see engine cut off and stow to slow down to the target height. The fireball and burn away seen are because the engines are run fuel rich, and I believe use skin cooling where the mixture is even more fuel rich around the sides of the bell using the fuel to absorb and take away heat cooling the bell’s skin. The rocket then sits on a bit of this unburnt fuel, burning it away. A challenge here is keeping the rocket balanced and stable while all of these wights shift and the engine realign to the new center.
At T 4:30 the vapor from the engine preburners that power the turbines nicely shows the rocket reaching hover and side flying before the belly flop. The big vapor burst is condensation due to pressure changes.
And we’re falling and we’re falling.
At T 6:30 we get engine restart. One good, two good, ugh hard flip around, this right here is the big test, does moving all this non static mass around off balance and rip it apart? No! All good! Just need engine three and... green, I don’t think it’s supposed to be, BOOM! Nope, it wasn’t.
So why the boom.
Because we know so quickly and they aren’t going back to the drawing board I would consider this test 100% successful. As the fuel is pumped from the tanks something needs to take its place, a rocket tank going glug, glug, glug, is a soon to be exploding rocket, so a high pressure tank of helium is used to keep the fuel and oxidizer tanks at pressure. In pressure fed engines and pumps they are used to force the fuel into the combustion chamber. For some reason a tank on the fuel side of things was at too low a pressure leading to a very oxidizer rich mixture being pumped through the third engine. Now we get to learn why rockets run a little fuel rich as the oxidizer turns the engine itself into fuel, the green being from some copper. Two potentially under performing engines wasn’t quite enough and as the rocket people like to say and RUD or Rapid Unscheduled Disassembly occurred.
Re: Drive by science
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